It is useless to give a greater number of examples of the alterations that have happened on the surface of the globe. Fire, air, and water, produce continual changes, which become very considerable by time. It is not from general causes alone, whose effects are periodical and regular, that the sea successively takes the place of the earth, and forsakes its own dominions. There are a number of particular causes which contribute to these mutations, such as earthquakes, inundations, sinking of mountains, &c. Thus the most solid thing, at least to our conception, like the rest of nature, undergoes continual and perpetual vicissitudes. CONCLUSION OF THE _THEORY OF THE EARTH_. By the proofs we have given in Articles VII. and VIII. it appears certain that the whole of the present dry land was formerly covered by the sea. It appears also as certain, from Article XII. that the flux and reflux, and other motions of the ocean, continually detach, from the side and the bottom of the sea, shells and matters of every kind, some part of which are deposited in other places in form of sediments, and which are the origin of the parallel and horizontal strata every where to be met with. We have proved in Article IX. that the inequalities of the globe have been caused by the motion of the sea, and that mountains have been produced by the successive masses and heapings of the sediments we have just described. It is evident by Article XIII. that the currents, which at first followed the direction of these inequalities, afterwards gave to them all the figure which they at present preserve; that is, that alternate correspondence of the saliant angles always opposed to the returning angles. It appears likewise by Articles VIII. and XVIII. that the greatest part of the matters which the sea has detached from its sides and bottom were, when deposited as sediments, in form of a fine impalpable powder, which perfectly filled the cavities of the shells, whether it was of the same nature or only analogous to that with which they were composed. It is certain, from Article XVII. that the horizontal strata which have been produced by the accumulation of sediments, and which at first were in a soft state, acquired hardness in proportion as they became dry, and that this drying has produced perpendicular clefts, which cross the horizontal strata.